1. Field of the Invention
This invention relates generally to a wheeled vehicle designed to turn about a vertical axis. In particular, the invention relates to powered utility riding vehicles of the type useful for construction, airport servicing operations, plowing, warehouse utility vehicles, wheelchairs, or any vehicle where rotation-in-place steering is advantageous.
2. Description of Prior Art
Prior art vehicles are known for turning with a zero turning radius, or so called xe2x80x9cturning on the spot.xe2x80x9d U.S. Pat. No. 3,938,608 describes a vehicle with a single center mounted pivoting drive motor that is rotated about a vertical axis in order to change directions of the vehicle. The ""608 vehicle is supported with three or more swivel wheels located at equal radial distances from the center wheel. The ""608 outer profile is in the shape of a rectangle and has appendages that make close proximity maneuvering impossible next to another object such as a post or another vehicle. Furthermore, the ""608 vehicle lacks tractive force because of the single drive wheel. Furthermore, a single drive wheel must be rotated in order to change the vehicle direction, and although the single drive wheel can be turned to direct the vehicle in any direction, it does not provide directional stability for the case where a force is exerted on the vehicle from an angle to the line of intended travel. For example, a force against the ""608 vehicle at a 20xc2x0 angle to the right or left of the line of travel would force the single ""608 wheel to skid, causing loss of directional control.
Many prior art material handling vehicles, such as snow plows, use conventional vehicles designed for on-road use, equipped with a hydraulically powered plow blade attached to the front of the vehicle. Conventional vehicles are typically configured with two axles, one in front, the other in the rear. The rear axle is fixed to the vehicle and provides motive force; two additional wheels are located at the front end of the vehicle, each being steerable and connected together to provide steering of the vehicle. Since there is a distance between the fixed rear drive wheels and the axis of the steerable wheels at the front end of the vehicle, a turning radius is required that far exceeds the space actually occupied by the vehicle itself. The longer the distance between front and rear axles, the larger the turning radius that is required to change directions of the vehicle. A large turning radius makes maneuvering around tight areas difficult and often dangerous.
Another method for steering is embodied in a second category of prior art material handling vehicles, such as fork lifts. These vehicles, designed primarily for warehouse use, usually have two axles, with the rear axle having smaller, steerable wheels and the front axle having larger, non-steerable wheels. These vehicles may have smaller turn radii than the conventional on-road vehicles, because they have a shorter distance between the front and rear axles. Also, the rear wheels are often capable of turning at large angles. Typical minimum outside turn radii range from sixty to one hundred inches. In the case of fork lifts, it is advantageous to have as small a turn radius as possible; a smaller turn radius allows a narrower isle width and a concomitant increase in usable floor space for storage in a given warehouse.
Other prior art material handling vehicles, such as those with buckets used for moving earth and the like, use a concept called skid steering to obtain a zero turn radius. Vehicles using skid steering are called xe2x80x9cskid steers.xe2x80x9d Skid steers consist of two axles each with powered, non-steerable wheels. All four wheels rotate in a plane parallel to the vehicle""s longitudinal axis. Turning the skid steer is accomplished by rotating the two wheels on the left side of the vehicle at a different speed or in a different direction than the two right wheels.
Rotating the two left wheels at the same speed but in the opposite direction as the two right wheels turns the vehicle about a vertical axis located in the geometrical center of the four wheels, that is, along a zero turn radius. However, the wheels are not in line with the turn. They are dragged transversely across their normal straight line of travel, because the axles are not located on the vertical turn axis. On soft ground, such as turf, this method of turning is usually adequate, but on asphalt or concrete, skid steering results in lurching, scuff marks, and high tire wear.
With prior art material handling vehicles, an operator must often move in reverse to maneuver in tight spaces. Even with a zero turn radius skid steer, an operator often cannot turn in place because of the swing radius of the bucket. Operators are required to look over their shoulders in order to back up. In a congested location, hazards from reversing are increased. A need exists for a material handling vehicle that requires less square footage for its footprints as well as the space required for maneuvering so that operator safety and the safety of the surroundings are enhanced.
A primary object of this invention is to provide a service vehicle that has enhanced maneuverability.
Another object of the invention is to provide a service vehicle that can turn on the spot without skid steering and be of the smallest physical size relative to the space it occupies.
Another object of the invention is to provide a service vehicle which reduces the risk of accidents which may result in damage or injury to equipment or operating personnel.
Another object of the invention is to provide a service vehicle having an outer perimeter that defines an outer imaginary cylinder that encloses any equipment or appendages rigidly mounted on the vehicle thereby enhancing its capability to maneuver the vehicle without impacting objects external to the vehicle.
Another object of the invention is to provide a service vehicle with utility tools mounted thereon for materials handling.
Another object of the invention is to provide a service vehicle that can be used for towing, plowing, pushing, sweeping, vacuuming, brushing, or lifting with a high degree of maneuverability.
Another object of the invention is to provide a vehicle that can turn on the spot, maneuver easily in limited spaces such as blind or interior corners, and maneuver around varying arcs such as curved curbs or cul-de-sacs and about obstructions such as posts, parked vehicles and buildings.
Another object of the invention is to provide a vehicle for pushing, plowing, lifting, or moving various solid materials such as snow, soil, gravel, or other materials which can be pushed by a blade or brush or vacuum or blower or scooped and lifted by a bucket scoop or forklift.
Another object of the invention is to provide a vehicle capable of plowing snow, ice, soil, etc. in continuous sweeping motions without stopping or reversing direction which minimizes lost load unproductive time.
Another object of the invention is to provide a vehicle for scooping, lifting and transporting buckets of snow, soil or the like with a zero turn radius without skid steering and without lifting the load high above the ground with a cantilevered lifting arm.
Another object of the invention is to provide a vehicle for moving palletized materials from one location to another with reduced maneuvering room, making it unnecessary to reverse and change directions as in the case of moving a pallet in a warehouse from one position on an isle laterally to another position on the same isle.
Another object of the invention is to provide a forklift that can transport a pallet either in front, to the side, or behind the driver thereby providing an unobstructed view for the driver.
Another object of the invention is to provide a vehicle having a lifting capability that is largely supported by an independent set of wheels, thereby reducing the amount of ballast or counterweight required to offset a load being transported.
The objects identified above along with other features and advantages of the invention are incorporated in a vehicle that provides unique maneuverability and efficiency, due to a combination of its characteristics including its shape and the configuration of its drive wheels. When the vehicle is combined with a radial movable hitch to its circular frame, such combination provides for free circumferential attachment to utility tools such as forks, buckets, plows, brushes, blowers, sweepers, and the like for material handling with minimal space required for maneuverability and safety of operation.
The vehicle includes a frame with a perfectly round outer ring about its perimeter having no external appendages. The ring has a perfect, unobstructed smooth circular surface defined by a vertical axis of the vehicle and a constant radius about the axis. The vehicle has two independent drive wheels located on a horizontal axis which intersects the vertical axis. Each wheel is at exactly the same distance from the vertical axis, with each wheel having the capability to move independently and at infinitely variable speeds in forward and reverse directions. Thus, the vehicle can move in any direction by rotating the axis of the drive wheels perpendicular to the desired direction of travel. By applying motive force to the wheels in the appropriate direction and speed, the vehicle can turn and move in any direction perpendicular to the axis of the drive wheels within the area covered by its circumference. The vehicle can rotate about the vertical axis to any radial heading without changing its original footprint. Accordingly, the vehicle requires a true zero turning or maneuvering radius, and thus requires only the space that it occupies in which to maneuver in any direction. The xe2x80x9cfootprintxe2x80x9d is the area on the ground below the vehicle when it is at rest. The vehicle requires no maneuvering space beyond the area or footprint covered by the vehicle itself. The space required of the vehicle is no greater than that of a conventional vehicle with a drive axle and a steering axle.
In one embodiment of the invention, the vehicle has upper and lower rails on the round outer ring which support a trolley. The trolley includes a plurality of cams, precision wheels or rollers that are rotatably coupled to the upper and lower rails of the outer ring so that the trolley can move freely around the entire circumference of the outer ring of the vehicle. The trolley is the point of attachment for a utility tool, such as a bucket or plow, to the vehicle.
The trolley is able to freely rotate about the round outer ring, but it contains castors which come into contact with the ground. The operator of the vehicle in this configuration positions the vehicle relative to the tool on tool trolley by keeping the vehicle behind the tool. The motion is similar to backing up a vehicle with a towed trailer, except the operator is facing in the direction of motion. For example, if a snow plow assembly is attached at the tool trolley in front of the vehicle, the operator is able to steer the snow plow blade by slightly turning the vehicle to the right or the left. If the blade is allowed to get too far from the front center of the vehicle, its tendency is to pass down the side of the vehicle to the rear. In this case, the operator must xe2x80x9cturn into the bladexe2x80x9d to regain a position firmly behind the blade. An operator is able to quickly maneuver the snow plow blade in the same manner that a window washer expertly wields a squeegee. When a utility tool is stationary, the vehicle can move with respect to the stationary tool until a desired heading of the vehicle is achieved. The tool trolley can alternatively be fixed to the frame in various positions for those applications where it is desirable not to allow the trolley to freewheel. In a third embodiment, the tool trolley is affirmatively positioned relative to the vehicle frame by actuators, such as electric or hydraulic motors.
The trolley has top, bottom and side plates which form a box hitch assembly. The sides of the box hitch assembly include two outriggers, each of which support a swivel caster. The casters provide support for both a portion of the vehicle weight and most of the weight of the utility tool and load, if any, attached to the box hitch assembly. In the case of a soil bucket or fork lift, the box hitch assembly also supports a lifting tower with guides and lifting apparatus that supports and guides the bucket or forks which carry the load. The lifting tower provides for the vertical lift, tilting action, and support for scissor extension of the load bearing forks.
The caster wheels mounted at either end of the box hitch assembly provide stability for the round vehicle when positioned at various locations about the circumference of the vehicle either in-line with the direction of the drive wheels or at a position perpendicular to the axis of the drive wheels. Thus, the vehicle is capable of transporting the attachment and its load in any position about the circumference of the vehicle, with the caster wheels providing the stability and load bearing capacity for the attachment.
The vehicle can move omni-directionally about a given point, change directions with zero maneuvering room beyond the physical footprint of the vehicle, and push or carry material with precise control. Such capabilities reduce the operating space on the ground required to move or handle an object being manipulated, thus increasing operating efficiency. Safety is increased because the operator of such a vehicle, positioned directly at the center of the vehicle, can always be facing the direction the vehicle is moving, never having to back up and look backward.